ABSTRACT
Medical ultrasound is a non-invasive, portable, extremely safe, inexpensive, highly valuable diagnostic tool especially when compared with X-ray and magnetic resonance imaging (MRI). But ultrasound has some limitation in distinguishing between diseased and healthy tissue. This limitation has led to the development of contrast agents. The primary goal of these contrast agents is to enhance the diagnostic image, so they can be used for targeted drug delivery. Polymeric microcapsules have many advantages, such as they are stable, provide a good surface to adsorb or carry the drug, and have good shelf life stability. Protein microspheres (PMs) have a wide range of biomedical applications, including their use as echo contrast agents for sonography, MRI, contrast enhancement, and oxygen or drug delivery. In this entry, we will discuss about ultrasound-assisted synthesis and coating of PM and other polymeric ultrasound contrast agents (UCAs). Proteins are dissolved in a liquid, which is then irradiated with intense ultrasound to induce acoustic cavitation. When the bubbles are heated during the rapid collapse, water vapor in the bubble is dissociated into OH radicals. These radicals cause the protein molecules to cross-link and a solid, spherical, protein shell is formed where the bubble once existed. The shells can be manufactured by filling with liquid or gas—liquid-filled spheres can be used for targeted or time released drug delivery and air-filled spheres are used as echo contrast agents in medical ultrasound.
